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Rubidium (Rb) deposits mostly occur in the South China and Central Asia orogenic belts and are often closely associated with highly differentiated granites. This study investigates a newly‐discovered giant Rb deposit at Gariatong in the Central Lhasa terrane in Tibet. Detailed field studies and logging data revealed that the Rb mineralization mainly occurs in monzogranite and is related to greisenization. LA‐ICP‐MS U‐Pb dating of zircon yielded ages of 19.1 ± 0.2 Ma and 19.0 ± 0.2 Ma for greisenized monzogranite and fresh monzogranite, respectively. The monzogranites are characterized as strongly peraluminous, with high contents of SiO2, Al2O3, K2O and Na2O as well as a high differentiation index. They are enriched in light rare earth and large ion lithophile elements with significant negative Eu anomalies and depleted high field‐strength elements. Petrological and geochemical features of these ore‐related monzogranites suggest that they are highly fractionated S‐type granites, derived from remelting of crustal materials in a post‐collisional setting. The geochemistry of zircon and apatite points to a low oxygen fugacity of the ore‐related monzogranite during the magma's evolution. The discovery of the Gariatong Rb deposit suggests that the Central Lhasa terrane may be an important region for rare metal mineralization. [ABSTRACT FROM AUTHOR]

The Baingoin batholith is one of the largest granitic plutons in the North Lhasa terrane. Its petrogenesis and tectonic setting have been studied for decades, but remain controversial. Here we report data on geochronology, geochemistry and isotopes of Early Cretaceous granitoids within the Baingoin batholith, which provide more evidence to uncover its petrogenesis and regional geodynamic processes. The Early Cretaceous magmatism yields ages of 134.4–132.0 Ma and can be divided into I‐type, S‐type and highly fractionated granites. The I‐ and S‐type granites exhibit medium SiO2, high K2O/Na2O with negative εNd(t) and εHf(t) values, whereas, the albite granites have very high SiO2 (79.04%–80.40%), very low K2O/N2O, negative εNd(t) and a large variation in εHf(t). Our new data indicate that these granitoids are derived from unbalanced melting in a heterogeneous source area. The granodiorites involved had a hybrid origin from partial melting of basalt‐derived and Al‐rich rocks in the crust, the porphyritic monzogranites being derived from partial melting of pelitic rocks. The albite granites crystallized from residual melt separated from K‐rich magma within the 'mush' process and underwent fractionation of K‐feldspar. We believe that the Early Cretaceous magmatism formed in an extensional setting produced by the initial and continuous rollback of a northward‐subducting slab of the NTO. [ABSTRACT FROM AUTHOR]

The Tibetan Plateau is a product of the continental collision between the Indian and Asian plates along the Indus-Yarlung suture zone that started in the early Cenozoic. This collision initially produced stress at the collisional boundary and later propagated with time on both the Indian plate and Asian plate. Many studies have reported tectonic deformation in the Himalayas representing the immediate response of continental collision on the Indian side near the collisional boundary. However, there have been only few studies on the early Cenozoic shortening structures in the Lhasa block that forms the southernmost part of the Asian plate. In this study, we performed Ar/Ar geochronology of syntectonic muscovite from the Sinongduo thrust system in the central Lhasa block. The results show that the Sinongduo thrust system was active in the Early Eocene. We interpret the Sinongduo thrust system as an immediate response to the India-Asia collision in the Lhasa block. This study reconciles the early Cenozoic India-Asia collision with the lack of tectonic response in the Lhasa block. [ABSTRACT FROM AUTHOR]

[Display omitted] • Accessory minerals geochemistry characteristics are affected by prior or cocrystallizing minerals. • The Cl contents in melts are important for forming porphyry Cu-Au deposits. • Zircon and apatite geochemistry combination is useful for refining targets in the SLT. The products of long-lasting magmatism (ca. 170 Myr) related to the northward subduction of the Neo-Tethys Ocean are preserved in the southern Lhasa subterrane (SLT). However, only a few large porphyry Cu–Au deposits related to these igneous rocks have been discovered in the Xiongcun ore concentration area. Here, we present zircon and apatite data on Jurassic fertile suites (FS), barren suites (BS), and recently proposed prospecting target suites (PTS) in the SLT, intending to present a case study of the regional-scale porphyry metallogenic potential. The zircon geochemical data with Rayleigh fractionation modeling show that the zircon geochemical characteristics of the FS and PTS were affected by high proportions of amphibole and titanite crystallization, whereas the zircon geochemistry of the BS displays the effects of plagioclase fractionation or mixing with the least evolved melts. The zircon Ce4+/Ce3+ and Eu/Eu* values cannot be used to trace the oxygen fugacity of the magma due to prior or simultaneous mineral crystallization. However, the zircon Ce/Ce* and Ce/Nd ratios may be used as semiquantitative measures of the magma redox conditions. This result is similar to that calculated by the new magmatic oxybarometer using trace elements in zircon, showing that the FS (ΔFMQ = 1.21 ± 0.42) and PTS (ΔFMQ = 1.29 ± 0.51) have higher oxygen fugacity levels than the BS (ΔFMQ = 0.40 ± 0.88). The melt S contents estimated from magmatic apatites are lower in the FS and PTS than in the BS, which is attributed to prior anhydrite crystallization under high oxygen fugacity and low temperature conditions. The higher Cl in the melt of the FS (average 0.098 wt%) than in the melts of the PTS (average 0.045 wt%) and BS (average 0.04 wt%) shows that elevated Cl contents in melts are likely important for forming porphyry Cu–Au deposits. The combined geochemical characteristics of zircon and apatite suggest that a high oxygen fugacity (ΔFMQ > 1.2), prior or concurrent anhydrite crystallization, and high zircon Eu/Eu* (>0.6), Ce4+/Ce3+, and (Yb/Dy) N values can be used to refine potential porphyry Cu–Au targets on a regional scale in the SLT. High melt Cl contents and apatite MnO and Pb contents can effectively indicate fertile suites at the deposit scale. [ABSTRACT FROM AUTHOR]

• The Sinongduo deposit is the first discovered low-sulfidation epithermal deposit. • The Pb-Zn mineralization is mainly concentrated in the range of 60.9–63.7 Ma. The Sinongduo Ag-Pb-Zn deposit is the first documented low-sulfidation epithermal deposit in Tibet and located on the southern side of the Longge'er-Gongbujiangda arc fault belt of the Lhasa terrane. The Ag-rich base metal veins and relatively low-grade breccias and stockworks in the Sinongduo deposit occur in the Paleocene high-potassium calc-alkaline to shoshonitic series volcanic rocks, including rhyolitic welded tuff breccia and volcanic breccia, rhyolitic ignimbrite, rhyolitic crystal fragment tufflava, rhyolite, and rhyolitic tuff. A nearly N-S-trending fault is the most important ore-controlling structure in the deposit. Galena and sphalerite are the dominant ore minerals in quartz-sericite-illite ± adularia veins, with subordinate argentite, pyrargyrite, native silver, chalcopyrite, pyrite and tennantite. The most widespread silver minerals are argentite, pyrargyrite, pearceite and native silver, which occur in fissures in Fe-Mn carbonates, jasper and early sulfides. The mineralization process can be divided into a pre-ore stage, main ore stage, and post-ore stage, and the main metallogenic stage is divided into the galena substage, sphalerite substage and silver minerals substage. Microthermometric analyses of the primary liquid-rich and vapour-rich fluid inclusions (FIs) in the sphalerite (SpII), main ore stage quartz (QzII) and post-ore stage quartz (QzIII) of the Sinongduo deposit indicate that the FIs in SpII, QzII and QzIII are mainly homogenized at temperatures of 197.2–280.8 °C, 185.6–290.4 °C and 148.2–218.7 °C with salinities of 1.40–5.71 wt% NaCl equiv., 1.59–5.71 wt% NaCl equiv. and 2.07–8.94 wt% NaCl equiv., respectively. These data indicate that the deposit was formed in a low-temperature and low-salinity environment, corroborating an epithermal system of mineralization. The O and H isotope compositions of the ore-forming fluids (δ18O = −0.6 to −6.3‰; δD = −177 to −151‰) indicate there was a major contribution from a meteoric water component to metallogenesis. All of the Pb isotope data from the metal sulfides and country rocks in the Sinongduo deposit in this study are similar and imply a close genetic relationship. The δ34S values of galena and sphalerite exhibit narrow distributions, ranging from +4.1‰ to +5.6‰ and from +7.6‰ to +8.4‰ respectively, with average values of +5.0‰ and +8.1‰, respectively, suggesting a uniform source. The Ar-Ar ages determined from sericite in the quartz-sericite-illite-sulfide veins range from 60.9 ± 0.7 to 63.1 ± 0.7 Ma, showing that the timing of epithermal Ag-Pb-Zn mineralization in the study area is consistent with the eruption of the Dianzhong Formation volcanic rocks (DVR) (U-Pb dating, 65–62 Ma), which indicates a genetic relationship. The characteristics of FIs, the H-O-S-Pb isotope data and the mineralization ages suggest that the ore-forming fluids were primarily sourced from circulating meteoric water, while S and Pb were derived from the DVR. Our results, combined with previous data on the regional geology, ore geology, FIs, and tectonic setting, indicate that the Sinongduo Ag-Pb-Zn deposit was produced in an epithermal system that formed on the southern side of the Longge'er-Gongbujiangda fault-block uplift belt, following the northward subduction of the Neo-Tethyan oceanic plate beneath the Asian continent. [ABSTRACT FROM AUTHOR]

The Jiama deposit, located in the eastern part of the well-known Gangdese Metallogenic Belt on the Tibetan Plateau, is the largest porphyry Cu–polymetallic system in the region, with the largest exploration budget, and is economically viable in the Gangdese Belt to undergo large-scale development. The deposit is well preserved and has experienced little erosion. The proven resources of the deposit are 7.4 Mt Cu, 0.6 Mt Mo, 1.8 Mt Pb + Zn, 6.65 Moz Au, and 360.32 Moz Ag. The results presented in this paper are based on geological and tectonic mapping, geological logging, and other exploration work performed by members of the Jiama Exploration Project Team over a period of 6 years. We propose that the Jiama porphyry Cu–polymetallic system is composed of skarn Cu–polymetallic, hornfels Cu–Mo, porphyry Mo ± Cu, and distal Au mineralization. The development of skarn Cu–polymetallic orebodies at the Jiama deposit was controlled mainly by the contact zone between porphyries and marbles, an interlayer detachment zone, and the front zone of a gliding nappe structure. The hornfels Cu–Mo and porphyry Mo ± Cu orebodies were controlled mainly by a fracture system related to intrusions, and the distal Au mineralization resulted from late-stage hydrothermal alteration. On the basis of field geological logging, optical microscopy, and chemical analysis, we verify that the alteration zones in the Jiama deposit include potassic, phyllic, propylitic, and argillic alteration, with a local lithocap, as well as endoskarn and exoskarn zones. The endoskarn occurs mainly as epidote alteration in quartz diorite porphyry and granite porphyry, and is cut by massive andradite veins. The exoskarn includes garnet–pyroxene and wollastonite skarn, in which the mineralogy and mineral chemical compositions display an outward zonation with respect to the source porphyry. From the proximal skarn to the intermediate skarn to the distal skarn, the garnet/pyroxene ratio varies from > 20:1 to ~ 10:1 to ~ 5:1, the garnet color varies from red-brown to brown-green to green-yellow, and the average composition of garnet varies from Ad 80.1 Gr 18.9 (Sp + Py) 1.0 to Ad 76.3 Gr 23 (Sp + Py) 0.7 to Ad 59.5 Gr 39.5 (Sp + Py) 1.0 , respectively. The pyroxene is not as variable in composition as the garnet, and is primarily light green to white diopside with a maximum hedenbergite content of ~ 20% and an average composition of Di 88.6 Hd 8.9 Jo 2.5 . From the proximal skarn to the intermediate skarn to the distal skarn, the mineralization changes from Cu–Mo to Cu ± Mo to Pb–Zn ± Cu ± Au ores, respectively. The wollastonite skarn displays no zonation and hosts mainly bornite mineralization. The Cu and Mo mineralization is closely related to the potassic and phyllic zones in the porphyry–hornfels. Zircons from four mineralized porphyries yield U–Pb ages of 15.96 ± 0.5 Ma, 15.72 ± 0.14 Ma, 15.59 ± 0.09 Ma, and 15.48 ± 0.08 Ma. The Re–Os ages of molybdenite from the skarn, hornfels, and porphyry are 15.37 ± 0.15 Ma, 14.67 ± 0.37 Ma, and 14.66 ± 0.27 Ma, respectively. The present results are consistent with the findings of previous research on fluid inclusions, isotopes, and other such aspects. On the basis of the combined evidence, we propose a porphyry Cu–polymetallic system model for the Jiama deposit and suggest a regional exploration strategy that can be applied to prospecting for porphyry-skarn mineralization in the Lhasa area. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Jiaoxi tungsten deposit comprises three stages, i.e., the oxide, sulfide, and fluorite stage. • Mineralization involves a low-salinity aqueous fluid. • Mineralization occurred as a result of fluid-fluid mixing induced cooling and dilution. The Jiaoxi deposit, located in the western part of the Lhasa terrane, is the first discovered Miocene (ca. 13 Ma) quartz vein-type tungsten deposit in this belt. Ore bodies mainly occur as wolframite-bearing veins hosted in the shales and granite. Three stages were identified for the formation of the Jiaoxi deposit, including the oxide stage (dominated by wolframite and quartz), the sulfide stage (quartz-sulfides veins) and the fluorite stage (late veins comprising fluorite, calcite, and quartz). Here, we investigate the genesis of this deposit based on fluid inclusion and H-O-S-Pb isotope studies. Fluid inclusion microthermometry and oxygen isotope data reveal that the wolframite precipitated from a moderate temperature (340–380 °C), low salinity (2.1–7.5 wt% NaCl equivalent) hydrothermal fluid at a depth of ∼ 6 km. The sulfides from the oxide and sulfide stage have uniform δ34S CDT values (+2.5 to + 3.7‰), and consistent Pb isotope compositions with the coeval granites (206Pb/204Pb: 17.866–18.789; 207Pb/204Pb: 15.555–15.743; 208Pb/204Pb: 37.157–39.335). The δ18O VSMOW value of the hydrothermal fluid decreased from the oxide (δ18O VSMOW = +7.2 to +14.2‰) to the fluorite stage (δ18O VSMOW = +2.1 to +5.7‰), indicating that the exsolved magmatic hydrothermal fluid mixed with meteoric water. This is also suggested by the positive correlation between the salinity and homogenization temperature of the aqueous fluid inclusions. LA-ICP-MS analysis of individual fluid inclusion reveals that the W concentrations of ore-forming fluid in the oxide stage (1.2–70.2 ppm) are much higher than those in the sulfide and fluorite stage (1.1–2.2 ppm) and show positive correlations with the homogenization temperatures and the Cl concentrations. We propose that fluid dilution and cooling due to fluid mixing played an important role during the wolframite precipitation in the Jiaoxi deposit. [ABSTRACT FROM AUTHOR]

Northern Tibet exhibits abundant placer gold deposits, with a longstanding history of mining activities. Despite the widespread placer gold occurrences, the reports on the primary rock gold deposits or occurrences remain scarce. The central Lhasa terrane in northern Tibet hosts well-developed Zenong Group volcanic rocks, indicating great potential for the exploration of porphyry-epithermal copper (gold) deposits. Here, we select the Dangreyongcuo area in this region to investigate its metallogenetic potentiality, through a comprehensive 1:50,000 stream sediment geochemical survey, analyzing 12 elements (Au, As, Sb, Ag, Te, Cu, Pb, Zn, W, Sn, Bi, and Mo), and a detailed geological mapping. We aim to identify gold-related mineralization anomalies and provide clues for further bedrock gold exploration in this region. Based on the stream sediment geochemical data, zones 1–4, have been delineated using single-element indicator Au and element association indicator Au + As + Sb, which was determined through robust principal component analysis (RPCA) and using the exploratory data analysis (EDA) method. Subsequent validation exercises evaluating these four delineated zones reveal that Zone 1, Xinlong-Langmeila area, is the most promising prospect due to its high element concentrations, large size, and marked coincidence of element assemblages (also referred to as high-large-coincidence anomalies; HLCAs) and its characteristics are in line with those of epithermal deposits. Notably, the Xinlong deposit represents the first documented epithermal gold deposit hosted within the Zenong Group volcanic rocks. The identification of this deposit offers valuable insights and strategic directions for the broader understanding of Zenong Group volcanic rocks across the central Lhasa terrane. Additionally, subsequent strategies have been proposed for mineral exploration at both Xinlong camp and regional scales. • Gold anomalies were detected in the western Dangreyongcuo area, Tibet. • Xinlong deposit is a newly discovered high-sulfidation epithermal gold deposit. • Xinlong gold deposit is linked to Zenong Group volcanic rocks. • Promising prospecting potential exists within regional Zenong Group volcanic rocks. [ABSTRACT FROM AUTHOR]

• The Shesuo deposit is related to the intermediate-felsic magmatism (117–112 Ma). • The Shesuo deposit associated with slab break-off during a postcollisional period. • The addition of reducing materials limited the magma fertility. The Bangong-Nujiang metallogenic belt is a newly discovered copper-polymetallic belt in the Tethyan domain. To date, the Shesuo skarn Cu-polymetallic deposit is the only productive Early Cretaceous Cu deposit in the middle segment of this belt. We conducted zircon U-Pb and molybdenite Re-Os dating of this deposit, and the results show that the Shesuo skarn Cu-polymetallic deposit formed at 117–112 Ma. Within the mining area, granodiorites and monzogranites are the main metallogenic granitic bodies. The petrogeochemical features imply that the granodiorites and monzogranites were derived from the partial melting of juvenile lower crust resulting from mantle-derived magmatic underplating, with the additional involvement of ancient crust in the magma chamber, whereas the monzogranites experienced significant fractional crystallization. The δ34S values of sulfide ores suggest that they were mainly sourced from the magma and slightly contaminated by surrounding strata. The Pb isotope compositions of sulfides and Re contents of molybdenite indicate that the metals were derived from the juvenile lower crust, with a small fraction from ancient crustal materials. Our study suggests that the generation of the Shesuo deposit was most likely triggered by slab breakoff during the southward subduction of the Bangong-Nujiang Ocean lithosphere. The Shesuo and Xiongmei deposits have low zircon Ce4+/Ce3+ and Eu N /Eu* ratios and low whole-rock average V/Sc, Sr/Y and (Eu N /Eu*)/Yb N ratios. We propose that these values are due to the input of reduced components, leading to the generation of metallogenic magmas with relatively low magmatic oxidation states and water contents and rendering the magmas infertile for later porphyry-skarn Cu formation in the Xiongmei area. [ABSTRACT FROM AUTHOR]

• Stable isotopes of fluids are comparable to those of typical orogenic gold deposits. • Ore fluids were likely generated through prograde metamorphic devolatilization. • Ore-forming materials were probably sourced from diagenetic pyrite at depth. • During transportation, gold-bearing fluids variably reacted with country rocks. Shangxu is an orogenic gold deposit in the Bangong-Nujiang suture zone, central Tibet, China, formed in the Early Cretaceous orogene, related to convergence and collision between the Qiangtang and Lhasa terranes. The mineralization at Shangxu is hosted by Jurassic turbidite sedimentary rocks of the Mugagangri Group, and is associated with a regional fault system. Hydrothermal minerals develop muscovite, carbonate, sulfides and chlorite. Hydrothermal fluids record three main hydrothermal stages based on mineral paragenesis. The earliest is barren quartz stage (H1), which is pre-ore. During the early mineralization quartz-pyrite stage (H2a), defined by massive quartz veins with minor euhedral pyrite and gold, hydrothermal fluids had a δ18O fluid of 6.1–6.4‰, δD of −74 to −116‰, δ13C CO2 of −5.4 to −7.6‰, and δ30Si of −0.1‰. In the quartz-pyrite-sulfides stage (H2b), characterized by abundant quartz, granular pyrite, muscovite with minor chalcopyrite, galena, sphalerite and gold, fluids had a δ18O fluid of 7–8.2‰, δD of −109 to −120‰, δ13C CO2 of −9.6‰ and δ30Si of −0.1 to −0.2‰. During the ankerite-sulfide stage (H3a), distinguished by abundant ankerite, muscovite, sulfides with minor quartz and chlorite, hydrothermal system had a fluid with δ18O fluid of 4.9–5.3‰, δD of −125.3‰, δ30Si of −0.1‰, δ13C CO2 of −12.4‰ in quartz inclusion fluid and δ13C CO2 of −2.7‰ in ankerite. The calcite-sulfide stage (H3b) is characterized by calcite, sulfides, with minor quartz and chlorite. Quartz formed earlier than calcite from a fluid having a δ18O fluid of 6.4‰, δD of −112.6‰, δ30Si of −0.1‰, and δ13C CO2 of −7.4‰, after which calcite precipitated from a hydrothermal fluid with δ18O fluid of 5.5–9‰, δ13C CO2 of −0.5 to −2.8‰. Hydrothermal fluids in H2b pyrite have 3He/4He ratios of 0.27–0.42Ra and 40Ar/36Ar ratios of 313–372. The stable isotope composition of hydrothermal fluids from the Shangxu gold deposit is similar to that of typical orogenic gold deposits. The early stage (H1), methane-bearing fluids were probably sourced from the basin sediments, leading to precipitation of early barren quartz veins and siderite alteration. From the quartz-sulfide stage (H2) to carbonate-sulfide stage (H3), hydrothermal fluids were likely derived from dissolution of the marine carbonate cement from sedimentary host rocks during metamorphism at depth. The decreasing δD and δ13C of the ore-forming fluids from early to late suggests mixing with δ13C-depleted oxidized graphite in sedimentary rocks, meteoric waters or reation between δD-depleted organic matters. Generally, these fluids were likely generated at depth through prograde metamorphic devolatilization of hydrous minerals in the deeper equivalents of the sedimentary rocks of the Mugagangri Group. Sulfur and gold, by inference, likely originated from sedimentary/diagenetic pyrite or the metasedimentary rocks between the greenschist and amphibolite facies, and migrated with the metamorphic fluids. During transportation to the site of deposition, gold-bearing fluids variably reacted with country rocks. [ABSTRACT FROM AUTHOR]

• Highly evolved parental magma controls formation of the Jiaoxi W deposit. • New geodynamic setting for Miocene granite-related W deposits in central Lhasa subterrane. • Mantle-derived melts play an important role in mobilizing the W from crust materials. The Jiaoxi deposit is the first Miocene quartz vein-type W deposit discovered in the western part of the Lhasa Terrane comprising with 39,000 metric tons of WO 3. The mineralization occurs in wolframite-bearing hydrothermal tensional quartz veins and is associated with Miocene granites. The mineralization event can be divided into an early quartz-oxide stage succeeded by a sulfide stage, and a final fluorite-carbonate stage. Magmatic intrusions at the deposit include biotite monzogranite porphyry, biotite monzogranite, granite porphyry, and muscovite granite at depth and show crystallization ages ranging between 14.5 and 13.7 Ma. Whole-rock geochemistry shows that the intrusions are alkali-rich peraluminous granites that experienced strong fractional crystallization. The most evolved muscovite granite has high W, Nb and Cs contents and is considered to be the source for mineralization. During the late crystallization stage of the highly fractionated muscovite granite, exsolved hydrothermal fluids interacted with the muscovite granite magma and migrated along extensional fractures forming the Jiaoxi deposit. Zircon grains from the granites show uniform ε Hf (t) values with a wide range between −7.08 and +3.87. The granites have initial Sr isotopic compositions ranging between 0.7094 and 0.7124 and negative ε Nd (t) values ranging between −4.9 and −9.4. The Sr-Nd-Hf isotope data indicate that the granites were derived from partial melting of a crustal source with minor contributions from the lithospheric mantle. The 3He/4He ratios for wolframite and pyrite vary between 0.30 and 0.74 Ra (Ra = 1.4 × 10–6 for air), confirming that W was mainly sourced from the crust. Collectively, the regional geology, geochronology and geochemistry, indicate that the Miocene post-collisional peraluminous granites and associated W mineralization were triggered by the roll-back and gradual break-off of the northward-subducting Indian continental lithosphere slab. The less evolved biotite monzogranite porphyry, which contains ore-bearing veins and local greisen alteration, appears to be unrelated to W mineralization. [ABSTRACT FROM AUTHOR]

The mechanisms triggering the emplacement of Cretaceous magmatic rocks related to Neo-Tethyan subduction in the southern Lhasa subterrane (SLT) remain controversial because geochronological, geochemical, and isotopic data from the Cretaceous magmatic rocks in the western portion of the SLT are lacking. This paper provides the first report indicating that the Dazhuqu hornblende gabbro and Xietongmen granite porphyry were generated in the Late Cretaceous (ca. 100 Ma and ca. 68 Ma, respectively) in the western portion of the SLT. The Dazhuqu hornblende gabbro is characterized by high MgO, Na2O, Cr, Co, and Mg# values, enrichment in light rare earth elements (LREEs) and large ion lithophile elements (LILEs), and depletion in high field strength elements with no Eu anomalies. The Xietongmen granite porphyry displays high SiO2, low MgO, Mg#, Cr, Co, and Ni, enrichment in LREEs and LILEs, flat heavy rare earth element (HREE) patterns and negative Eu anomalies. Zircons from the Dazhuqu hornblende gabbro and Xietongmen granite porphyry display high positive εHf(t) ranges from 11.79 to 14.91 and from 9.05 to 12.38, respectively. The Dazhuqu hornblende gabbro was produced by the partial melting of 12–15% garnet peridotite in the depleted mantle that was metasomatized by fluids released from the dehydrating subducted Neo-Tethyan oceanic slab. This magma was then emplaced at an upper crustal depth of 5.3–7.0 km. The Xietongmen granite porphyry was generated by the partial melting of underplated basaltic crust during the subduction of the Neo-Tethyan oceanic crust and formed in the presence of pyroxene, plagioclase, and minor hornblende in its magmatic source. In combination with previously published data from Cretaceous magmatic rocks in the SLT, our data suggest that the petrogenesis of the Dazhuqu hornblende gabbro was related to flat or low-angle slab subduction of the Neo-Tethyan oceanic crust during 109–97 Ma and that the formation of the Xietongmen granite porphyry was related to lithospheric delamination in the western portion of the SLT after ca. 68 Ma. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Zircon U–Pb dating indicates the emplacement of Ruocuo adakitic porphyries during the Early–Middle Jurassic (182–170 Ma). • Ruocuo adakitic porphyries were generated by the partial melting of the Neo-Tethys oceanic slab. • Formation of Early Mesozoic magmatic rocks in the southern Lhasa subterrane in a magmatic arc setting. • The northern Xigaze forearc basin has a potential for subduction-related porphyry Cu–Au mineralization. Abstract Jurassic adakitic rocks in the southern Lhasa subterrane are relatively rare, poorly documented, and their petrogenesis and geodynamic setting are unclear. To explore these issues, we present zircon U–Pb ages along with Hf isotopic, whole-rock geochemical, and Sr–Nd–Pb isotopic data for hornblende quartz diorite porphyry (HQDP) and quartz diorite porphyry (QDP) in the Ruocuo area, southern margin of the Lhasa terrane, Tibet. Zircon U–Pb dating for these rocks indicates that they were emplaced in the Early–Middle Jurassic (182–170 Ma). Geochemically, HQDP and QDP both show characteristics of adakites, with intermediate SiO 2 (60.62–65.63 wt% and 57.46–60.04 wt%, respectively), relatively high Al 2 O 3 (14.23–18.23 wt% and 18.32–20.14 wt%, respectively) and Sr (344–571 ppm and 514–614 ppm, respectively), and low Y (9.12–13.0 ppm and 11.0–14.9 ppm, respectively) and Yb (0.93–1.31 ppm and 1.08–1.52 ppm, respectively). In addition, they show relatively low ratios of (87Sr/86Sr) i (0.7038–0.7045), (206Pb/204Pb) i (18.31–18.42), (207Pb/204Pb) i (15.56–15.66), and (208Pb/204Pb) i (38.36–38.77) and relatively high values of ε Nd (t) (+5.54 to +6.33) and ε Hf (t) (+11.8 to +17.3). The Sr–Nd–Pb–Hf isotopes of HQDP and QDP are similar to those of the Yarlung Tsangpo ophiolites, indicating that they were predominantly generated by the partial melting of the subducted Neo-Tethys oceanic slab. The subducted Neo-Tethys oceanic slab-derived adakitic rocks that are present in the southern Lhasa subterrane provide strong evidence for proving the presence of oceanic subduction during the Early–Middle Jurassic. By combining our results with the previously reported results, we suggest that the Ruocuo adakitic rocks and Early Mesozoic (Late Triassic to Middle Jurassic) magmatic rocks in the southern Lhasa subterrane formed in a magmatic arc setting related to the northward subduction of the Neo-Tethys oceanic slab, that the initial subduction of the Neo-Tethys oceanic slab occurred prior to the Early Jurassic, and that the upwelling asthenosphere, triggered by the roll-back of the subducted Neo-Tethys oceanic slab, provided the heat that was required for slab melting. However, contrasting these results with the geochemical characteristics of the No. 2 deposit in the Xiongcun Cu–Au district leads us to consider that the Early–Middle Jurassic subducted oceanic slab-derived adakitic porphyries contain a greater potential for porphyry Cu–Au mineralization than the Early Mesozoic normal magmatic rocks in the southern Lhasa subterrane. Furthermore, mineralized Jurassic porphyry has been reported in the Ruocuo area, adjacent to the northern Xigaze forearc basin, indicating that the northern Xigaze forearc basin also has the potential for subduction-related porphyry Cu–Au mineralization. [ABSTRACT FROM AUTHOR]

The Bangbule skarn lead‐zinc (Pb‐Zn) deposit (>1 Mt Zn + Pb) is located in the western Nyainqentanglha polymetallic metallogenetic belt, central Tibet. Lenticular orebodies are all hosted in skarn and developed in the contact zone between the quartz porphyry and carbonate strata of the mid Paleozoic Middle to Upper Chaguoluoma Formation as well as in carbonate and sandstone beds of the Upper Paleozoic Laga Formation. As a newly discovered skarn deposit, the geological background and metallogenesis of this deposit remain poorly understood. Detailed petrological, geochemical and geochronological data of the ore‐related quartz porphyry, helps constrain the mineralization age and contributes to discussion on the ore genesis of the Bangbule deposit. Both endoskarn and exoskarn are identified in the Bangbule deposit. From quartz porphyry to carbonate formation, the exoskarn is zoned from proximal garnet skarn to distal pyroxene skarn. Zircon U‐Pb dating results show that the quartz porphyry formed at 73.9 ± 0.8 Ma. Geochemical analysis results show that the quartz porphyry has high contents of SiO2 (71.40–74.94 wt%) and K2O + Na2O (3.76–8.46 wt%) with A/CNK values of 0.69 to 1.06. Besides, the quartz porphyry is enriched in large ion lithophile elements (LILEs) and light rare earth elements (LREEs) and have low εNd(t) (from –8.25 to –8.19) and high initial (87Sr/86Sr)i values (0.713611–0.714478). Major, trace elements and whole‐rock F concentration analysis results from the endoskarn samples show higher TFe2O3, MgO, CaO, Pb + Zn, W, Sn, Mo and F etc., and lower alkalis (K2O, Na2O, Sr and Ba) than those of fresh quartz porphyry, indicating that the early ore‐forming fluids were an Ca‐Fe‐F‐enriched fluid. Massive ore in the proximal skarn might be related to the high F content in the magma, which lowered the solidus temperature of the quartz porphyry magma and caused a lower temperature of the ore‐forming fluids, as well as facilitating the precipitation of sphalerite and galena. Based on the geochemical characteristics presented in this study, we propose that the ore‐related quartz porphyry was formed by partial melting of crust materials with some juvenile crustal component input. The partial melting of the middle‐upper crust after the initial enrichment of lead and zinc elements are important for the formation of Pb‐Zn deposits. The case study of the Bangbule deposit has proven that there is still a crust‐derived magmatic source region in the western segment of the central Lhasa terrane. Therefore, there is still great potential for Pb‐Zn mineralization and Pb‐Zn exploration. [ABSTRACT FROM AUTHOR]

The Bangong–Nujiang suture zone (BNSZ), which separates the Gondwana-derived Qiangtang and Lhasa terranes, preserves limited geological records of the Bangong–Nujiang Ocean (BNO). The timing of opening of this ocean has been hotly debated due to the rare and complicated rock records in the suture zones, which span over 100 Ma from Carboniferous–Permian to Early Jurassic time, based on geological, palaeontological and palaeomagnetic data. A combination of geochemical, geochronological and isotopic data are reported for the Riasairi trachytes, central BNSZ, northern Tibet, to constrain its petrogenesis and tectonic settings. Zircon U–Pb dating by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) yields mean ages of 236 Ma. Geochemically, these rocks are high-K calc-alkaline with moderate SiO2 (59.1–67.5 wt%) and high K2O + Na2O (8.1–11.6 wt%) contents. They are enriched in light rare earth elements with negative Eu anomalies, and show enrichments in high-field-strength elements with positive 'Nb, Ta' anomalies, similar to the intra-continental rift setting-related felsic lavas from the African Rift System. The high positive zircon ϵHf(t) and bulk ϵNd(t) values, as well as high initial Pb isotopes, imply a heterogeneous source involving both asthenospheric and subcontinental lithospheric mantle. The field and geochemical data jointly suggest that the Riasairi trachytes within the Mugagangri Group were formed in a continental rift setting. We interpret that the continental-rift-related Riaisairi trachytic lavas as derived from the southern margin of the Qiangtang terrane, implying that the BNO would have opened by Middle Triassic time, well after the commonly interpreted break-up of the Qiangtang terrane from Gondwana. [ABSTRACT FROM AUTHOR]

The Bangong–Nujiang collision zone (BNCZ) is an ideal area for studying postcollisional magmatism. A series of late Early Cretaceous Cu‐bearing magmas are found in this collision zone, which has implications for studying the sources of postcollisional magmas. We completed detailed fieldwork and reported zircon U–Pb and Hf‐isotopic and whole‐rock geochemical data on the Daguo volcanics, Shesuo monzogranite‐granodiorites, and Xiongmei granodiorite porphyries, which represented different types of the Cu‐bearing rocks in the BNCZ. The Shesuo samples are characterized by high contents of SiO2, K2O, and total alkali, with high contents of heavy rare earth elements (HREEs) and Y, and are enriched in large‐ion lithophile elements (LILEs), depleted in Nb and Ta, with a marked negative Eu anomaly (0.29–0.92). The Xiongmei granodiorite porphyries are characterized by moderate SiO2 and MgO, high Al2O3 contents, depletion in Nb, Ta, Ba, Sr, and Ti, enrichment in LILEs, high HREEs and Y contents, and relatively low Sr/Y ratios. Both Shesuo monzogranites and Xiongmei granodiorites belong to calc‐alkaline I‐type magmas, which are associated with a wide range of zircon εHf(t) values (−15.3 to +5.8; −15.4 to +3.2). These geochemical features suggest that the Xiongmei granodiorite porphyries and Shesuo monzogranite‐granodiorites are derived from the melting of a juvenile mafic crust with ancient crustal contamination, and the juvenile mafic crusts are derived from a lithospheric mantle enriched by slab melt (including recycled subducting sediments). The Daguo basalt is derived from the partial melting of a mantle wedge metasomatized by subduction‐related fluids and/or melts and the involvement of asthenospheric mantle. The Daguo intermediate‐felsic rocks are derived from the partial melting of a juvenile crust from a metasomorphic mantle wedge. Our study implies that the genesis of these Cu‐bearing magmas is associated with slab break‐off at the end of the southward subduction of the Bangong–Nujiang Ocean lithosphere. In addition, the postcollisional magmas are multisourced, with a juvenile component from either the metasomorphic lithosphere mantle or the juvenile crust, an ancient crustal component and a subducted‐related component from the recycled subducting sediments, the subducted slab, and/or the asthenosphere. [ABSTRACT FROM AUTHOR]

Early Mesozoic (Late Triassic to Middle Jurassic) igneous rocks in the southern Lhasa subterrane, Tibet, record important information on the early tectono-magmatic evolution of the Neo-Tethys Ocean. This paper presents petrological, geochronological, and geochemical data for the Xiongcun Formation ignimbrites, to constrain the petrogenesis and tectonic setting of these rocks in the southern Lhasa subterrane. The Xiongcun Formation is dominated by andesitic and dacitic rocks. These rocks yield Early Jurassic (195–176 Ma) zircon U Pb ages and display typical arc-like geochemical signatures, being enriched in large-ion lithophile elements (e.g., Rb, Ba, and U) and depleted in high-field-strength elements (e.g., Nb, Ta, and Ti). Sr–Nd–Pb–Hf isotopic compositions are highly depleted. These chemical and isotopic data suggest that the Xiongcun Formation ignimbrites probably formed in an intra-oceanic island arc setting related to the northward subduction of the Neo-Tethys oceanic slab. The parental magmas were derived from a depleted mantle source modified by fluids released from the Neo-Tethys oceanic slab. Combined with previously reported data, we suggest that the volcanic rocks in the Early Jurassic Xiongcun and Yeba formations of the southern Lhasa subterrane were generated by a single subduction system, but developed on oceanic and continental crust, respectively. Unlabelled Image • Xiongcun Formation (XF) volcanism occurred during the Early Jurassic period. • XF ignimbrites were generated by the partial melting of a depleted mantle source. • XF ignimbrites formed in an intra-oceanic island arc setting. • XF and Yeba Formation volcanism were likely generated by a single subduction system. [ABSTRACT FROM AUTHOR]

The Early Mesozoic (ca. 240–185 Ma) magmatic rocks in the central Lhasa subterrane (CL) provide crucial insight into the geodynamics of the Early Mesozoic orogenic assembly in the Lhasa Terrane. Here we present an integrated geochemical and geochronological study combining new and published data of the Early Mesozoic magmatism in the CL to reveal the geodynamic processes and magmatic responses involved in this orogeny. The here studied A-type granodiorites from the Luoza batholith display zircon U-Pb ages of 199 Ma, and zircon saturation temperatures of 833–857 °C. In addition, zircons have highly enriched radiogenic Hf isotope compositions (ε Hf (t) = −20.1 to −4.3). The Luoza granodiorite samples have high (87Sr/86Sr) t ratios between 0.7174 and 0.7209, and negative ε Nd (t) values between −9.5 and − 9.1. We propose the granodiorites were generated via partial melting of ancient basement rocks with minor inputs of basaltic melts (~10%). The here studied monzogranites and syenogranites from the Menba batholith are normal calc-alkaline and highly fractionated I-type granites that yield zircon U-Pb ages from 197 to 184 Ma and 187 Ma, respectively. The zircon grains of both rock types have relatively higher ε Hf (t) values (−13.8 to +0.5) than those of the Luoza granodiorites. The Menba monzogranites have (87Sr/86Sr) t ratios between 0.7062 and 0.7081, and ε Nd (t) values between −6.9 and − 3.4. The calculated ε Nd (t) values for the Menba syenogranites range from −4.5 to −4.0. The isotope data set indicates that the Menba granitoids were generated via mixing of ancient crustal melts and mantle-derived magmas (~50%). The high-temperature and low-pressure conditions indicated by the Early Jurassic Luoza A-type granitoids are geodynamically linked to a post-collisional setting. This evidence, in combination with Early Mesozoic magmatism identified within the CL, clearly displays a transitional conversion from ca. 240–210 Ma S-type-dominated to ca. 210–185 Ma I-type-dominated magmatism. This distinct change in magmatism reflects the geodynamic change from a syn -collisional to a post-collisional setting, involving the breakoff of the Sumdo Paleo-Tethys oceanic slab at ca. 210 Ma. The Early Mesozoic magmatic belt within the CL may record the orogenic assembly between the central and southern Lhasa subterranes, which represents the important evidence for closure of the Sumdo Paleo-Tethys Ocean. Consequently, the Early Mesozoic magmatic belt within the CL reveals that the Sumdo Paleo-Tethys Ocean extended at least from the Luoza area, central Lhasa Terrane, to the easternmost end of the Lhasa Terrane. • Early Jurassic (ca. 200–185 Ma) A-type and I-type granitoids in the CL. • The different sources and petrogenesis of Early Jurassic granitoids in the CL. • Early Jurassic granitoids in the CL were emplaced under a post-collisional setting. • Early Mesozoic magmatism in the CL records a post-subduction tectonic evolution. • Post-subduction tectonic events are used to trace the scale of extinct ocean basin. [ABSTRACT FROM AUTHOR]